This invention relates to vulcanizable polyoctenamer molding compositions having improved flow properties together with satisfactory mechanical properties in the vulcanizates produced therefrom.
It is known that articles of vulcanized elastomers, as compared to those of thermoplastic synthetic resins, exhibit additionally high elasticity as well as the usual comparable mechanical strength properties. After the vulcanizable macromolecules have been fixed by crosslinking bridges, this high elasticity ranges from the second order transition temperature up to the thermal decomposition temperature and spans, depending on the type of elastomer employed, temperatures ranging from about -100.degree. C. to about 30 200.degree. C. The enormous deformation capacity with a pronounced restoring force which can be observed within these limits, i.e., the reformation of the original force after a dimensional change without any essential permanent deformation, have securely established elastomers in fields of use not accessible in such a comprehensive range to any other material.
As compared to the manufacture of molded parts from thermoplastic synthetic resins, the processing of elastomers into vulcanized shaped objects requires a substantially higher expenditure due to the inherent characteristics of of the raw materials employed. In addition to the unavoidable crosslinking process, the raw materials, due to their substantially higher viscosity, must be subjected to mixing and deformation steps necessitating a high energy consumption. In order to conduct such steps on a technical scale, relatively heavy and expensive machinery must be utilized. The enormous amount of heat liberated by strong shear effects during the course of such process steps makes it compulsory to conduct the process discontinuously and in several stages. The considerable expenses resulting from the investment in machines and labor, which greatly burden the economy of the production of elastic articles, have previously resulted in displacement of the elastomers by nonelastomers in many fields of utilization, at the cost of relinquishing the typical elastomer properties which would often otherwise be desirable; e.g., see W. F. Watson (RAPRA) Revue generale du Caoutchuc et des Plastiques SV (1973) No. 6, pp. 463-465. For this reason, many attempts have been directed toward a simplification of the processing of elastomers with the goal of extensively adapting them to the processing characteristics of thermoplastic synthetic resins; e.g., see Klaus v. Hoerde, "Gummi/Asbest/Kunststoffe" (Rubber, Asbestos, Synthetic Resins) 4/1972, p. 332.
However, to solve this problem, it is not enough merely to lower the viscosity average molecular weights of the elastomers employed. The production of low-viscosity polymers, e.g., of butadiene or isoprene and/or copolymers thereof with styrene, does not present any technical problems. However, when such polymers of lower molecular weights are vulcanized, the lowering of the molecular weights is accompanied by a steady drop in the physical and mechanical properties of the finished articles. These properties are imparied to an intolerable degree if the molecular weight and viscosity of the used polymers have been reduced to optimal levels from the processing viewpoint.
In one attempt to avoid these disadvantages, low-molecular weight elastomers having functional terminal groups have been proposed, which undergo chain lengthening during the customary vulcanization process, i.e., in addition to the vulcanization crosslinking taking place, a lengthening of the molecule chain occurs; e.g., see S. H. Morall, "Gummi/Asbest/Kunststoffe" 7/72, pp. 658-662.
Apart from the fact that such attempts have not yet resulted in materials leading to satisfactory vulcanizate properties, especially as they are required for example in the manufacture of vulcanized tires, the manufacture of such elastomers having functional terminal groups is complicated and accordingly relatively expensive. The storage of the polymers used as the vulcanizable raw materials is problematic due to the terminal groups thereon which render the functionally modified polymers in most cases sensitive to atmospheric oxygen and moisture.